Disquiet among National MPs looks set to delay planned changes to health and safety law, with the Government poised to park the bill in a select committee for two more months to try and iron out contentious issues.

Recommended changes to the law were due to be reported back from the committee this week, Prime Minister John Key said on Monday.

But after National's Tuesday caucus meeting a well-placed source said approval would likely be sought for an extension to the select committee's deliberations.

The draft bill, prompted by the Pike River coal mine tragedy, was already set to be watered down in the face of a possible revolt by back bench Government MPs. That would likely include an exemption for small businesses from some provisions.

So, they appear to have got what they want in the caucus room. But will they get what they want in the House? Because no matter what Judith Collins and her followers think, the bill can't become law unless it has the support of either the Maori Party or United Future (or, I suppose, NZ First). And there's no real indication that they'd support extreme right-wing policies on health and safety, any more than they'd support them on the RMA. Which is likely to cause even more frustration on the right...